1. Field of the Invention
The present invention relates to a movement disorder monitor, and a method of measuring the severity of a subject's movement disorder. The present invention additionally relates to a drug delivery system for dosing a subject in response to changes in severity of a subject's symptoms.
2. Technical Background
Movement disorders include Parkinson's disease (PD) and essential tremor. The treatments can involve pharmaceutical interventions, fetal cell transplants, surgery, or deep brain stimulation in some of these disorders. The efficacy of these interventions is often judged by the interventions ability to alleviate patient symptoms and improve their quality of life. With Parkinson's disease for example, the major symptoms that affect quality of life are tremor, bradykinesia, rigidity, and dyskinesia. These symptoms are partly responsible for the subject's functional disability and social embarrassment.
Tremors are involuntary muscle contractions characterized by oscillations of a body part. Tremor of the hands can be cosmetically upsetting and affect functional tasks such as grasping of objects. Resting tremors usually occur at frequencies of approximately 4-7 Hz while the frequency of action of postural tremor is higher, usually between 9-11 Hz. Tremor is a symptom often targeted by treatment. The standard clinical method for analyzing rest and postural or action tremor is qualitative assessment by a clinician and assignment of a score.
Bradykinesia refers to delays or hesitations in initiating movements and slowness in executing movements. The standard clinical method for analyzing bradykinesia is qualitative assessment by a clinician and assignment of a score. This score is assigned while the subject completes a repetitive finger-tapping task, a repetitive hand opening-closing task, and a pronation-supination task. Objective assessment by this means is difficult and variable. It has been found that movement rate and time are useful in better characterizing bradykinesia.
Rigidity occurs because muscles of the body are overly excited. The neurons involved in inhibition circuitry have died due to Parkinson's disease and muscles may receive continuous excitation. Rigidity causes the joints of the subject to become stiff and decreases range of motion. During normal movement, an agonist muscle contracts while the antagonist muscles relax. However, due to the constant motor unit input, the antagonist is unable to relax. Again, the standard clinical method for analyzing rigidity is qualitative assessment by a clinician and assignment of a score. To do so a clinician passively moves the subject's joints through a range of motion while the subject relaxes.
Dyskinesia is one of the most common and disabling complications of chronic drug therapy. Dyskinesias are wild involuntary movements that typically occur when the benefit from the drug therapy is at its maximum. Clinical assessment of dyskinesias typically relies on self-reporting by the subject. There is a great need to objectively quantify these involuntary movements in view of the growing number of pharmacologic agents and surgical procedures to improve dyskinesia.
While standard clinical evaluation involves qualitative assessment of these symptoms, recently some efforts have been made to quantify symptoms of movement disorders. Accelerometers and gyroscopes have been used individually to quantify some of these movement disorder symptoms, however, alone each sensor has limitations. Accelerometers operate in response to the local gravitational field; therefore they often have problems in separating changes in linear acceleration from rotation. Further, results of a second integration required to obtain linear position are often contaminated with noise, making measurement difficult at best. Gyroscopes measure angular velocity independent of gravity with a good frequency response; however, static angular position cannot be measured accurately due to DC drift characteristic with these devices. Combining the information from both accelerometers and gyroscopes can provide a more accurate method of quantifying motion.
Currently, no commercially available system provides a means to objectively quantify the severity of movement disorder symptoms in real-time. Furthermore, many of these systems are bulky and cannot easily be worn by a subject during normal daily activities so as a result can only be used to monitor the subject in an intermittent fashion. In addition, some of these systems are tethered, which reduces patient safety, limits home monitoring capabilities, and does not allow for recording of some movement disorder symptoms. Finally, none of the current systems have clinician interface software, which quantifies symptoms such as tremor, bradykinesia, rigidity, and dyskinesias and relates them to standard rating scales such as the Unified Parkinson's Disease Rating Scale (UPDRS). Additionally, none of these systems have clinical video instruction and real-time clinical video feedback.
It is therefore an object of the present invention to provide a system for accurately quantifying symptoms of movement disorders. It is still another object of the present invention to provide a system, which accurately quantifies symptoms utilizing both kinetic information and electromyography (EMG) data. It is still another object of the present invention to provide a wireless movement disorder system that can be worn continuously to provide continuous information to be analyzed as needed by the clinician. It is still further another object of the present invention to provide a movement disorder system that can provide analysis in real-time. It is still further another object of the present invention to provide a movement disorder system to allow for home monitoring of symptoms in subject's with these movement disorders to capture the complex fluctuation patterns of the disease over the course of days, weeks or months. It is still further an object of the present invention to maximize subject safety. It is still further an object of the present invention to provide a system with clinical video instruction and real-time clinical video feedback. It is still further an object of the present invention to provide a treatment delivery system that can monitor symptoms in subject's and deliver treatment in response to those symptoms. Finally it is the object of the present invention to provide remote access to the clinician or physician.